Phase change materials for enhanced heat transfer fluid performance

ABSTRACT

A composition for enhanced heat transfer fluid performance. The composition includes at least one base heat transfer fluid. The at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process. The heat transfer process includes a heated zone and/or a cooled zone. The one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes. The base heat transfer fluids can exhibit liquid crystal behavior (e.g., heat transfer fluids having nematic, smectic or discotic liquid crystals). A method for conducting heat transfer in a heating and/or cooling system using the compositions comprising the base heat transfer fluids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/611,057, filed on Dec. 28, 2017, the entire contents of which are incorporated herein by reference.

In addition, this application also claims the benefit of related U.S. Provisional Application Nos. 62/611,072 and 62/611,081, both filed on Dec. 28, 2017, the entire contents of which are also incorporated herein by reference.

FIELD

This disclosure relates to high performance heat transfer fluids based on heat rejection and adsorption during fluid phase changes. Also, this disclosure relates to a method for conducting heat transfer in a heating and/or cooling system using a heat transfer fluid based on heat rejection and adsorption during fluid phase changes. The heat transfer fluids can exhibit liquid crystal behavior.

BACKGROUND

Transfer of heat from local high temperature zones is a critical performance feature of lubricants and circulating fluids. In lubricated systems, examples of heat sources that require cooling include, but is not limited to, heat generated by combustion processes, heat resulting from friction within a lubricated contact, heat created by energy sources, and heat used in manufacturing processes (e.g., paper and steel making).

In some cases, specialized fluids are used for the sole purpose of removing heat from high temperature zones. Examples include coolants used in internal combustion engine applications, and transformer oils used to cool electrical distribution equipment. More recently, requirements to cool the battery and power generation systems in electric and hybrid vehicles has emerged as another application for fluids aimed at removing heat.

Traditional fluids remove heat via combinations of conductivity and convection mechanisms. The heat removed is a function of fluid properties such as heat capacity and thermal conductivity, system design including selection of materials that determine the heat flow across fluid/surface interfaces, and operational factors such as fluid flow rate and temperature difference between fluid and the high temperature zone requiring cooling.

Improving heat transfer is an emerging need as energy density of systems and equipment increases. Improving thermodynamic efficiency is often coupled with higher operating temperatures. There are emerging requirements to provide cooling fluids for hybrid and electric vehicles. Currently traditional cooling fluids, including formulated lubricants are being used. These have limited property ranges that will be extended using the liquid crystal approach.

Other approaches include the use of higher density fluids and suspension of solid nano particles. The range of performance of the former is relatively limited. Use of nano particles has looked promising but relies on being able to disperse sufficient quantity of the particles. There are also health and safety concerns regarding the use of engineered nano particles.

Performance of conventional heat transfer fluids is related to fluid properties such as specific heat capacity and conductivity. For most fluids, these properties fall within a narrow range and limit potential heat transfer performance.

A major challenge in heat transfer fluids is the development of alternate pathways to heat transfer performance for emerging needs as energy density of systems and equipment increases.

SUMMARY

This disclosure relates to high performance heat transfer fluids based on heat rejection and adsorption during fluid phase changes. Also, this disclosure relates to a method for conducting heat transfer in a heating and/or cooling system using a heat transfer fluid based on heat rejection and adsorption during fluid phase changes. The heat transfer fluids can exhibit liquid crystal behavior.

This disclosure relates in part to a composition for enhanced heat transfer fluid performance. The composition comprises at least one base heat transfer fluid. The at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process. The heat transfer process comprises a heated zone and/or a cooled zone. The one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.

This disclosure also relates in part to a blend composition for enhanced heat transfer fluid performance. The blend composition comprises: (i) at least one base heat transfer fluid, and (ii) one or more lubricating oils comprising a Group I, Group II, Group III, Group IV, or Group V oil. The at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process. The heat transfer process comprises a heated zone and/or a cooled zone. The one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.

This disclosure further relates in part to a method for conducting heat transfer in a heating and/or cooling system. The method comprises: (a) providing a composition comprising at least one base heat transfer fluid in the heating and/or cooling system; and (b) conducting heat transfer between the at least one base heat transfer fluid and the heating and/or cooling system. The least one base heat transfer fluid undergoes one or more phase changes in the heating and/or cooling system. The one or more phase changes increase heat removal from the heating system and/or increase heat rejection in the cooling system, as compared to heat removal from a heating system and/or heat rejection in a cooling system having a base heat transfer fluid that does not undergo one or more phase changes.

This disclosure yet further relates in part to a method of heat transfer comprising: (a) providing an object to be heated or cooled; and (b) transferring heat to or from the object to be heated or cooled by a composition comprising at least one base heat transfer fluid. The least one base heat transfer fluid undergoes one or more phase changes. The one or more phase changes increase heat removal from the object and/or increase heat rejection in the object, as compared to heat removal from an object and/or heat rejection in an object by a base heat transfer fluid that does not undergo one or more phase changes.

It has been surprisingly found that, in accordance with this disclosure, enhanced heat transfer fluid performance is achieved using a composition comprising a base heat transfer fluid that undergoes one or more phase changes, in which the one or more phase changes increase heat removal from a heated zone and/or increase heat rejection in a cooled zone of a heat transfer process, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.

In particular, it has been surprisingly found that, in accordance with this disclosure, enhanced heat transfer fluid performance is achieved using a composition comprising a base heat transfer fluid that exhibits liquid crystal behavior (e.g., a heat transfer fluid having smectic and/or discotic liquid crystals), in which the liquid crystal behavior increases heat removal from a heated zone and/or increase heat rejection in a cooled zone of a heat transfer process, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not exhibit liquid crystal behavior.

It has been surprisingly found that, in accordance with this disclosure, enhanced heat transfer fluid performance and fluid flow properties are achieved using a blend composition comprising a base heat transfer fluid that undergoes one or more phase changes, in which the one or more phase changes increase heat removal from a heated zone and/or increase heat rejection in a cooled zone of a heat transfer process, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes. The blend composition comprises (i) the at least one base heat transfer fluid, and (ii) one or more lubricating oils comprising a Group I, Group II, Group III, Group IV, or Group V oil.

In particular, it has been surprisingly found that, in accordance with this disclosure, enhanced heat transfer fluid performance and fluid flow properties are achieved using a blend composition comprising a base heat transfer fluid that exhibits liquid crystal behavior (e.g., a heat transfer fluid having smectic and/or discotic liquid crystals), in which the liquid crystal behavior increases heat removal from a heated zone and/or increase heat rejection in a cooled zone of a heat transfer process, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not exhibit liquid crystal behavior. The blend composition comprises (i) the at least one base heat transfer fluid, and (ii) one or more lubricating oils comprising a Group I, Group II, Group III, Group IV, or Group V oil.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows DSC results for S2 liquid crystal during heating cycle showing heat adsorption during phase change, in accordance with the Examples.

FIG. 2 shows DSC results for the same S2 liquid crystal during cooling cycle showing heat rejection during phase change, in accordance with the Examples.

FIG. 3 graphically depicts results from a falling body high pressure viscometer conducted on S2 liquid crystal, in accordance with the Examples.

FIG. 4 graphically depicts similar results to FIG. 3 for a 25% liquid crystal/75% 4cSt PAO blend, in accordance with the Examples.

FIG. 5 shows DSC heating cycle results for 25%, 50% and 75% blends of liquid crystal in 4 cSt PAO showing shift in heat adsorption behavior versus the pure liquid crystal (FIG. 1), in accordance with the Examples.

FIG. 6 shows DSC cooling cycle results for 25%, 50% and 75% blends of liquid crystal in 4 cSt PAO showing shift in hear rejection versus the pure liquid crystal (FIG. 2), in accordance with the Examples.

FIG. 7 shows DSC data for the 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate LC3 liquid crystal (Example 3).

FIG. 8 shows DSC data for the 4-pentylphenyl 4-(heptyloxy)benzoate L4 liquid crystal (Example 4).

FIG. 9 shows DSC data for the 4-pentylphenyl 4-(heptyloxy)benzoate L4 liquid crystal (Example 4).

FIG. 10 shows DSC data for the 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate L6 liquid crystal (Example 6).

DETAILED DESCRIPTION Definitions

“About” or “approximately.” All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

“Liquid crystal” fluids mean highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds. The various liquid crystal phases may be characterized by the type of ordering. Among these are namely nematic, smectic or discotic phases.

“Smectic liquid crystals” refer to hydrocarbon molecules that are arranged in layers, with the long molecular axes approximately perpendicular to the laminar planes. The only long range order extends along this axis, with the result that individual layers can slip over each other (soap-like in nature). A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

“Major amount” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil.

“Minor amount” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil.

“Essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm).

“Flat viscosity” temperature performance as it relates to the lubricant base stocks and lubricating oils disclosed herein mean that the viscosity does not vary as a function of temperature over a temperature range from 20 to 100 deg. C.

“Other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof.

“Other mechanical component” as used in the specification and the claims means an electric vehicle component, a hybrid vehicle component, a power train, a driveline, a transmission, a gear, a gear train, a gear set, a compressor, a pump, a hydraulic system, a bearing, a bushing, a turbine, a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, or a bearing including a journal, a roller, a tapered, a needle, and a ball bearing.

“Hydrocarbon” refers to a compound consisting of carbon atoms and hydrogen atoms.

“Alkane” refers to a hydrocarbon that is completely saturated. An alkane can be linear, branched, cyclic, or substituted cyclic.

“Olefin” refers to a non-aromatic hydrocarbon comprising one or more carbon-carbon double bond in the molecular structure thereof.

“Mono-olefin” refers to an olefin comprising a single carbon-carbon double bond.

“Cn” group or compound refers to a group or a compound comprising carbon atoms at total number thereof of n. Thus, “Cm-Cn” group or compound refers to a group or compound comprising carbon atoms at a total number thereof in the range from m to n. Thus, a C1-C50 alkyl group refers to an alkyl group comprising carbon atoms at a total number thereof in the range from 1 to 50.

“Carbon backbone” refers to the longest straight carbon chain in the molecule of the compound or the group in question. “Branch” refer to any substituted or unsubstituted hydrocarbyl group connected to the carbon backbone. A carbon atom on the carbon backbone connected to a branch is called a “branched carbon.”

“SAE” refers to SAE International, formerly known as Society of Automotive Engineers, which is a professional organization that sets standards for internal combustion engine lubricating oils.

“SAE J300” refers to the viscosity grade classification system of engine lubricating oils established by SAE, which defines the limits of the classifications in rheological terms only.

“Base stock” or “base oil” interchangeably refers to an oil that can be used as a component of lubricating oils, heat transfer oils, hydraulic oils, grease products, and the like.

“Lubricating oil” or “lubricant” interchangeably refers to a substance that can be introduced between two or more surfaces to reduce the level of friction between two adjacent surfaces moving relative to each other. A lubricant base stock is a material, typically a fluid at various levels of viscosity at the operating temperature of the lubricant, used to formulate a lubricant by admixing with other components. Non-limiting examples of base stocks suitable in lubricants include API Group I, Group II, Group III, Group IV, and Group V base stocks. PAOs, particularly hydrogenated PAOs, have recently found wide use in lubricants as a Group IV base stock, and are particularly preferred. If one base stock is designated as a primary base stock in the lubricant, additional base stocks may be called a co-base stock.

All kinematic viscosity values in this disclosure are as determined pursuant to ASTM D445. Kinematic viscosity at 100° C. is reported herein as KV100, and kinematic viscosity at 40° C. is reported herein as KV40. Unit of all KV100 and KV40 values herein is cSt unless otherwise specified.

All viscosity index (“VI”) values in this disclosure are as determined pursuant to ASTM D2270.

All Noack volatility (“NV”) values in this disclosure are as determined pursuant to ASTM D5800 unless specified otherwise. Unit of all NV values is wt %, unless otherwise specified.

All pour point values in this disclosure are as determined pursuant to ASTM D5950 or D97.

All CCS viscosity (“CCSV”) values in this disclosure are as determined pursuant to ASTM 5293. Unit of all CCSV values herein is millipascal second (mPa·s), which is equivalent to centipoise), unless specified otherwise. All CCSV values are measured at a temperature of interest to the lubricating oil formulation or oil composition in question. Thus, for the purpose of designing and fabricating engine oil formulations, the temperature of interest is the temperature at which the SAE J300 imposes a minimal CCSV.

All percentages in describing chemical compositions herein are by weight unless specified otherwise. “Wt. %” means percent by weight.

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. The phrase “major amount” or “major component” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil. The phrase “minor amount” or “minor component” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil. The phrase “essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm). The phrase “other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof.

The compositions of this disclosure containing the base heat transfer fluids have advantageous characteristics for corrosion inhibition, and a high thermal capacity to protect the fluid from degradation at high temperatures. A base heat transfer fluid means the major constituent of the heat transfer fluid and typically is a base stock or base oil.

In accordance with this disclosure, liquid crystals offer an alternative and additive mechanism to conventional heat transfer fluids, and are fully miscible with conventional hydrocarbon heat transfer fluids. The alternative and additional mechanism provided by the high performance heat transfer fluids based on heat rejection and adsorption during fluid phase changes increases the heat transfer performance. This effect can also work as a performance booster for conventional heat transfer fluids.

Further, in accordance with this disclosure, classes of materials have been identified that undergo complex solid/solid, solid/liquid and liquid/liquid phase changes. An example of these materials include liquid crystals which are partially ordered materials that can undergo multiple phase changes while remaining in a semi-solid/liquid state. When such fluids undergo a phase change, the physical properties of the fluid can change and can become anisotropic or return to isotropic behavior. During such phase changes, the liquid crystal may reject or adsorb heat. It has been surprisingly found that this feature of phase change behavior can be used to enhance heat transfer mechanisms, increasing the ability of the fluid to remove heat. This mechanism works in addition to any heat adsorption that occurs as the fluid is heated up, and thus adds to the total heat removal process.

This phase change behavior can be exploited in a traditional cooling circuit system in which a fluid is circulated in a closed system. In this case, the fluid is pumped through a high temperature zone and as a result is heated up. The total energy removed can be estimated from the fluid's specific heat capacity, the temperature rise that the fluid undergoes and the mass of fluid flowing through the system. The fluid is then passed through a system designed to reject the heat returning the fluid to its original temperature for recirculation into the hot zone. In accordance with this disclosure, an additional heat transfer mechanism associated with the phase changes can increase the heat removal from the hot zone and/or heat rejection during cooling.

This disclosure provides high performance heat transfer fluids based on heat rejection and adsorption during fluid phase changes. A specific example includes fluids that exhibit liquid crystal behavior.

Compositions that exhibit liquid crystal behavior include base heat transfer fluids that contain liquid crystals (e.g., smectic and/or discotic liquid crystals) as described herein.

Heat transfer fluids that exhibit liquid crystal behavior can be blended with lubricating oil base fluids in order to optimize fluid flow properties while retaining the heat transfer benefits associated with the liquid crystal phase changes, as described herein. In an embodiment, the heat transfer fluids that exhibit liquid crystal behavior can be blended with lubricating oil base fluids, to form bimodal blends.

In addition to the base heat transfer fluids, the compositions of this disclosure can contain additives. Illustrative additives useful in the heat transfer fluids of this disclosure include, for example, corrosion inhibitors, thermal stabilizers, viscosity modifiers, pH stabilizers or buffers, antiscaling additives, biocides, and the like.

Corrosion inhibitors are preferably selected from tolyl triazole, benzotriazole, aspartic acid, sebacic acid, borax, molybdic oxide, sodium molybdate dihydrate, morpholine, or a combination of two or more thereof. Sodium molybdate dihydrate is an advantageous additive in aluminium (Al) containing systems since it works especially well as an Al corrosion inhibitor. The total amount of corrosion inhibitor in the heat transfer fluid is preferably from 0.01 to 0.5% (w/w).

Thermal stabilizers are preferably selected from tetra (2-hydroxypropyl) ethylenediamine (also known as quadrol polyol), polyethyleneglycol, pentaerythritol or a combination of two or more thereof. The total amount of thermal stabilizer in the heat transfer fluid is preferably from 0.1 to 1% (w/w). Sodium hydroxide may also be added as a stabilizer in an amount of less than 0.05% (w/w), although this is in addition to any thermal stabilizer that may be present. Sodium hydroxide serves to stabilize the glycerine component of the composition and is preferably present in an amount of at least 0.01% (w/w).

A viscosity modifier in the heat transfer fluid assists in controlling the viscosity of the fluid to an acceptable level. The specific viscosity modifier and quantities of viscosity modifier used can have the advantage of providing a desired viscosity and also advantageous characteristics with regard to the inhibition of corrosion and the stability of the heat transfer fluids, in particular thermal stability. They also can permit the use of known anti-corrosion and anti-scaling additives. Illustrative viscosity modifiers include, for example, triethanolamine, a glycerol ethoxylate, and the like. The total amount of viscosity modifier in the heat transfer fluid is preferably from 0.1 to 1% (w/w).

Illustrative pH stabilizers or buffers include, for example, triisopropanol amine, borax, and the like. The total amount of pH stabilizer or buffer in the heat transfer fluid is preferably from 0.01 to 0.5% (w/w).

Illustrative antiscaling additives include, for example, sodium polyacrylate polymer, and the like. The total amount of antiscaling additive in the heat transfer fluid is preferably from 0.01 to 0.5% (w/w).

Illustrative biocides include, for example, nipacide, and the like. The total amount of biocide in the heat transfer fluid is preferably from 0.01 to 0.5% (w/w).

The additives useful in this disclosure do not have to be soluble in the heat transfer fluids. Insoluble additives in base fluids can be dispersed in the heat transfer fluids of this disclosure.

The types and quantities of performance additives used in combination with the instant disclosure in heat transfer fluids are not limited by the examples shown herein as illustrations.

When heat transfer fluid compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function.

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of heat transfer fluid additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The base heat transfer fluid as disclosed herein is described in relation to the % (w/w) of each of the components added. It will be appreciated that the balance of these components is preferably the base heat transfer fluid. During manufacture, some unavoidable impurities may be introduced into the fluid as well. Preferably such unavoidable impurities should be less than 5% (w/w), preferably less than 1% (w/w), more preferably less than 0.1% (w/w) and most preferably less than 0.01% (w/w). Ideally there are no unavoidable impurities present.

With respect to the compositions of this disclosure, the at least one heat transfer fluid has a freezing point of at least greater than about −50° C., or greater than about −45° C., or greater than about −40° C., as determined by ASTM D1777-17, a boiling point of greater than about 100° C., or greater than about 125° C., or greater than about 150° C., as determined by ASTM D1120-17, and a flash point of at least 50° C., or at least 60° C., or at least 70° C., as determined by ASTM D93-16a.

The heat transfer process is carried out at a temperature from about −40° C. to greater than about 80° C., or from about −35° C. to greater than about 90° C., or from about −30° C. to greater than about 100° C., and/or a pressure from about 50 MP to about 500 MP, or from about 60 MP to about 475 MP, or from about 70 MP to about 450 MP.

Base Heat Transfer Fluids Containing Liquid Crystals

The base heat transfer fluids of this disclosure can be comprised of liquid crystals such as S2 or analogs with differing R group side chains or differing core structure still containing two rings, at least one aromatic, with or without additional additives or base stocks present, to give lower traction compared to non-liquid crystal hydrocarbon fluids of the same viscosities. The liquid crystals do not contain any heteroatoms.

The base heat transfer fluids of this disclosure can comprise one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon group alkyl group or alkoxy group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, or —CH2O—; and m and n are independently 0, 1, 2 or 3. The base heat transfer fluids have a kinematic viscosity of about 2 cSt to about 28 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 12 cSt at 100° C., as determined according to ASTM D445.

Illustrative liquid crystals useful in this disclosure include, for example, those represented by the formula:

In particular, illustrative liquid crystals useful in this disclosure include, for example, 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, 4-(trans-4-propylcyclohexyl)-ethylbenzene, and mixtures thereof.

Other liquid crystals useful in this disclosure additionally include, 4-pentylphenyl, 4-methylbenzoate, 4-pentylphenyl 4-ethylbenzoate, 4-pentylphenyl 4-propylbenzoate, 4-pentylphenyl 4-butylbenzoate, 4-pentylphenyl 4-(octyloxy)benzoate, 4-pentylphenyl 4-methoxybenzoate, 4-pentylphenyl 4-ethoxybenzoate, 4-pentylphenyl 4-propoxybenzoate, 4-pentylphenyl 4-butoxybenzoate, 4-pentylphenyl 4-pentoxybenzoate, and mixtures thereof.

Other liquid crystals include 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate.

Also, the base heat transfer fluids of this disclosure can comprise one or more discotic liquid crystals. The one or more discotic liquid crystals are represented by the formula:

A-(R3)_(n)

wherein A is a mono-ring or a multi-ring aromatic group, R3 is the same or different and is a substituted or unsubstituted, hydrocarbon group having from about 2 to about 24 carbon atoms, and n is a value from about 1 to about 12. The base heat transfer fluids have a kinematic viscosity of about 2 cSt to about 28 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 12 cSt at 100° C., as determined according to ASTM D445.

Illustrative discotic liquid crystals useful in this disclosure include, for example, those represented by the formula:

In particular, illustrative discotic liquid crystals useful in this disclosure include, for example, hexakis(octylthio)benzene, and mixtures thereof.

The liquid crystal materials of this disclosure access a state of matter that is both fluid and anisotropic in nature—essentially these materials are not solids, which possess a highly ordered crystalline structure and lack ability of translation of molecules in any direction, and they are not liquids, which are characterized by their lack of order but intermolecular forces that overcome kinetic energy, keeping them in a condensed phase. Instead liquid crystals can be considered “partly ordered” in that in some direction(s) they may appear ordered, and in others they may appear disordered. These materials are therefore anisotropic in nature, and the amount of ordering seen depends on from which angle they are viewed.

Accordingly, as used herein, “liquid crystal” means highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds.

As used herein, “smectic liquid crystals” refers to hydrocarbon molecules that are arranged in layers, with the long molecular axes approximately perpendicular to the laminar planes. The only long range order extends along this axis, with the result that individual layers can slip over each other (soap-like in nature). A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

As used herein, “discotic liquid crystals” refers to hydrocarbon molecules that are arranged in layers. Discotic phase liquid crystals include disc-shaped crystals in columnar phases. Their molecules have a symmetric branched formula which can be approximated by a flat disc. Discotic crystals demonstrate the layered arrangement like smectic crystals. Their molecules lie in the layer planes forming close hexagonal packing.

The liquid crystal base oils of this disclosure conveniently have a kinematic viscosity, according to ASTM standards, of about 2 cSt to about 28 cSt (or mm²/s) at 40° C. and preferably of about 2.5 cSt to about 25 cSt (or mm²/s) at 40° C., often more preferably from about 2.5 cSt to about 20 cSt at 40° C. Also, the liquid crystal base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 1 cSt to about 12 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 10.5 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 10 cSt at 100° C.

Mixtures of liquid crystal base oils may be used if desired. Bi-modal, tri-modal, and additional combinations of mixtures of liquid crystal base oils and optional Group I, II, III, IV, and/or V base stocks may be used if desired. With mixtures of liquid crystal base oils and Group I, II, III, IV, and/or V base stocks, the liquid crystal base oil is present is an amount ranging from about 5 to about 99 weight percent or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition. Preferably, with mixtures of liquid crystal base oils and Group I, II, III, IV, and/or V base stocks, the liquid crystal base oil is present is an amount ranging from about 50 to about 99 weight percent or from about 55 to about 95 weight percent, preferably from about 60 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

The liquid crystal base oil typically is present in an amount ranging from about 5 to about 99 weight percent or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

Preferably, the liquid crystal base oil constitutes the major component of the engine, or other mechanical component, oil lubricant composition of the present disclosure and typically is present in an amount ranging from greater than about 50 to about 99 weight percent or from about 55 to about 95 weight percent, preferably from about 60 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

Blends of Base Heat Transfer Fluids and Lubricating Oil Base Fluids

A wide range of optional lubricating base fluids is known in the art. Optional lubricating base fluids that are useful in the present disclosure are natural oils, mineral oils and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and/or less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than about 120 and contain less than or equal to about 0.03% sulfur and greater than about 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or  >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Optional base oils for use in the heat transfer fluids of the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their volatility, stability, viscometric and cleanliness features.

The optional base oil is typically is present in an amount ranging from about 5 to about 99 weight percent or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition. The optional base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark-ignited and compression-ignited engines. The optional base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 2.5 cSt to about 18 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 12.5 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 10 cSt. Mixtures of synthetic and natural base oils may be used if desired. Bi-modal, tri-modal, and additional combinations of mixtures of Group I, II, III, IV, and/or V base stocks may be used if desired.

The blends of heat transfer base fluids and lubricating oil base fluids useful in the present disclosure may additionally contain one or more of the other commonly used performance additives as described herein.

The blends of heat transfer fluids that exhibit liquid crystal behavior with lubricating oil base fluids can optimize fluid flow properties while retaining the heat transfer benefits associated with the liquid crystal phase changes, as described herein.

The blends of heat transfer base fluids and lubricating oil base fluids useful in the present disclosure may additionally contain one or more of the other commonly used performance additives as described herein.

The heat transfer fluids of this disclosure can be used to heat or cool an object and can be used in heating and cooling systems for heating and cooling residential, commercial and industrial buildings. The heat transfer fluids can be used in an engine cooling system. To cool a vehicle having a radiator and an engine block, the heat transfer fluid is moved through the engine block to transfer heat from the engine block to the heat transfer fluid. The heat transfer fluid then moves through the radiator to transfer heat from the heat transfer fluid to the radiator and to air surrounding the radiator.

When used in a heating and cooling system for a building, the heat transfer fluid can be inserted into the pipes of the heating and cooling system. The heating or cooling systems can include a boiler, pipes, a radiator, and a pump. The heat transfer fluid is then moved into contact with the boiler so that heat is transferred from the boiler to the heat transfer fluid. The heat transfer fluid then moves through the radiators of the heating and cooling system and heat is transferred from the heat transfer fluid to the radiators. Heat is then transferred from the radiators to air surrounding the radiators and into the building to heat the air in the building.

The heat transfer fluids of this disclosure can be stored in steel, plastic, poly or stainless steel containers. The heat transfer fluids can be pumped from the storage container into the heating and cooling systems or the objects to be heated or cooled by most types of pumps well known in the art such as gear, air, diaphragm, roller, or piston.

The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES

Fluids were prepared as described herein.

The base fluids used were smectic liquid crystal base fluid (i.e., 4-(trans-4-heptylcyclohexyl)-pentylbenzene (referred to as “S2 liquid crystal”)) and PAO4 base fluid.

Testing results were obtained using differential scanning calorimetry (DSC) and a high pressure falling body viscometer.

FIG. 1 shows DSC results for S2 liquid crystal during heating cycle showing heat adsorption during phase change.

The DSC results shown in FIG. 1 reveal the heat adsorbed during a phase change that occurs between 14° C. to 17° C. for S2 liquid crystal during the heating cycle. In this experiment, the heat adsorbed was measured to be 100.4 J/g. For comparison, fluid heat capacity for lubricant range hydrocarbons is typically measured to be approximately 2.5 J/gK.

FIG. 2 shows DSC results for the same S2 liquid crystal during cooling cycle showing heat rejection during phase change. As shown in FIG. 2, there is an additional phase change occurring at much lower temperature.

Liquid crystal phase changes result in differences in rheological performance. These effects were examined using a high pressure falling body viscometer. At combinations of pressure and temperature, it was observed that the phase change was clearly identified by a discrete change in the viscosity response. FIG. 3 shows the line defining the boundary of one of the phase changes exhibited by S2 liquid crystal. The upper left is a region in which normal fluid like behavior occurs, and the lower right corresponds to the area in which flow becomes more restricted and semi-fluid like. This shows that the transition temperature can be controlled by changing the system pressure.

FIG. 3 graphically depicts results from high pressure viscosity measurements conducted on S2 liquid crystal. The line shows the points of transition associated with a phase change.

FIG. 3 graphically depicts results from a falling body high pressure viscometer conducted on S2 liquid crystal, in accordance with the Examples. At high temperature/low pressures, the fluid maintains viscous properties. At high pressures/low temperatures, the falling body remains suspended indicating that a phase transition has occurred resulting in mixed visco-elastic behavior. The line depicts the measured boundary between these phases as a function of temperature and pressure.

Experiments were conducted on blends of S2 liquid crystal in PAO. FIG. 4 shows a similar transition boundary as found for the pure liquid crystal. The boundary is shifted toward lower temperature and higher pressures. The results confirm that phase change behavior occurs in mixtures as well as the pure materials. FIG. 4 graphically depicts similar results to FIG. 3 for a 25% liquid crystal/75% 4cSt PAO blend, in accordance with the Examples. A similar phase change was observed and was shifted toward higher pressures. Results indicate phase change behavior occurs for mixtures.

FIG. 5 shows DSC heating cycle results for 25%, 50% and 75% blends of liquid crystal in 4 cSt PAO showing shift in heat adsorption behavior versus the pure liquid crystal (FIG. 1).

FIG. 6 shows DSC cooling cycle results for 25%, 50% and 75% blends of liquid crystal in 4 cSt PAO showing shift in hear rejection versus the pure liquid crystal (FIG. 2).

FIG. 7 shows DSC data for the 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate LC3 liquid crystal (Example 3). In the heating cycle, we see a phase transitions at 65.35° C. and 85.91° C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan reveals the existence of the liquid crystalline phase starting at 85° C. with super cooling.

FIG. 8 shows DSC data for the 4-pentylphenyl 4-(heptyloxy)benzoate L4 liquid crystal (Example 4). In the heating cycle, we see a phase transitions at 42° C. and 60° C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan reveals the existence of the liquid crystalline phase starting at 60° C. with super cooling.

FIG. 9 shows DSC data for the 4-pentylphenyl 4-(heptyloxy)benzoate L4 liquid crystal (Example 4). In the heating cycle, we see a phase transitions at 42° C. and 60° C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan reveals the existence of the liquid crystalline phase starting at 60° C. with super cooling.

FIG. 10 shows DSC data for the 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate L6 liquid crystal (Example 6). In the heating cycle, we see a phase transitions at 44° C. and 61° C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan reveals the existence of the liquid crystalline phase starting at 60° C. with super cooling.

The Examples show that liquid crystal phase change behavior can be used to design high performance heat transfer fluids. This principle can be applied to any system which undergoes a phase change which includes the class of materials known to exhibit liquid crystal behavior. In addition, the principle can work with other phase changes such as wax formation. The performance of these fluids will be controlled by the structure of the liquid crystal, system design and operation, and any blend components used in the final fluid.

Series of benzoate liquid crystals (LC3-6) were synthesized and characterized using spectroscopic and DSC measurements.

Series of benzoate esters (MWs 412, 396, 382, and 366) were synthesized by using alkyl or alkoxy substituted benzoic acid and alkyl or alkoxy substituted phenol to obtain ester products. In this series phenyl benzoate portion of the molecule was kept constant and flexible chain portion of the molecule was varied by either —CH2- group or —O— atom. Among various esterification reactions, esterification using DCC (dicyclohexylcarbodiimide) and DMAP (4-dimethylaminopyridine) catalyst was preferred as reaction can be carried out under mild reaction conditions (room temperature). The benzoic acid used were 4-(heptyloxy)benzoic acid and 4-heptylbenzoic acid and phenol used were 4-(hexyloxy)phenol and 4-pentylphenol. The four esters (L3, L4, L5 and L6) were characterized using NMR and DSC. All four products are found to be liquid crystals with varying phase transition temperature. Such study would allow one to develop structure activity and potentially can be used for model assisted synthesis of desired liquid crystal molecule.

Example 1. Synthesis of 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate LC3

4-heptylbenzoic acid (MW 220.31, 4.0 g, 18.16 mmol), 4-(hexyloxy)phenol (MW 194.27, 3.53 g, 18.16 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 3.75 g, 18.16 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.09 g, 0.73 mmol) were mixed in 40 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 5.21 g of white solid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.10 (dt, 2H, ArH), δ 7.30 (d, 2H, ArH), δ 7.10 and 6.92 (dt, dt, 2H, 2H, ArH), δ 3.96 (t, 2H, ArOCH₂—), δ 2.69 (t, 2H, ArCH₂—), δ 1.78 (quin, 2H, ArOCH₂CH₂—), δ 1.65 (quin, 2H, ArCH₂CH₂—), δ 1.47 (quin, 2H, ArOCH₂CH₂CH₂—) δ 1.40-1.22 (m, 12H, —CH₂—), δ 0.93-0.87 (t, t, 6H, CH₃—).

Example 2. Synthesis of 4-pentylphenyl 4-(heptyloxy)benzoate LC4

4-(heptyloxy)benzoic acid (MW 236.31, 4.0 g, 16.93 mmol), 4-pentylphenol (MW 164.24, 2.78 g, 16.93 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 3.49 g, 16.93 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.10 g, 0.85 mmol) were mixed in 60 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 4.36 g of white solid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.13 (dt, 2H, ArH), δ 7.21 (d, 2H, ArH), δ 7.09 and 6.96 (dt, dt, 2H, 2H, ArH), δ 4.04 (t, 2H, ArOCH₂—), δ 2.61 (t, 2H, ArCH₂—), δ 1.82 (quin, 2H, ArOCH₂CH₂—), δ 1.63 (quin, 2H, ArCH₂CH₂—), δ 1.47 (quin, 2H, ArOCH₂CH₂CH₂—), δ 1.41-1.27 (m, 10H, —CH₂—), δ 0.90 (t, 6H, CH₃—).

Example 3. Synthesis of 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate LC5

4-(heptyloxy)benzoic acid (MW 236.31, 6.0 g, 25.39 mmol), 4-(hexyloxy)phenol (MW 194.27, 6.93 g, 35.67 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 6.29 g, 30.47 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.31 g, 2.54 mmol) were mixed in 90 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 7.92 g of white solid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.12 (dt, 2H, ArH), δ 7.09 (dt, 2H, ArH), δ 6.97-6.90 (dt, dt, 4H, ArH), δ 4.03 and 3.95 (t, t, 2H, 2H, ArOCH₂—), δ 1.85-1.75 (m, 4H, ArOCH₂CH₂—), δ 1.51-1.42 (m, 4H, ArOCH₂CH₂CH₂—), δ 1.41-1.27 (m, 10H, —CH₂—), δ 0.93-0.88 (t, t, 6H, CH₃—). ¹³C NMR (CDCl₃, 100 MHz) δ 165.4, 163.6, 156.9, 144.5, 132.3, 122.6, 121.8, 115.2, 114.4, 68.5, 68.4, 31.9, 31.8, 29.4, 29.3, 29.2, 26.1, 25.9, 22.8, 14.23, 14.20.

Example 4. Synthesis of 4-pentylphenyl 4-heptylbenzoate LC6

4-heptylbenzoic acid (MW 220.31, 5.0 g, 22.69 mmol), 4-pentylphenol (MW 164.24, 5.6 g, 34.04 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 5.62 g, 27.23 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.28 g, 2.27 mmol) were mixed in 90 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 7.06 g of white milky liquid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.10 (d, 2H, ArH), δ 7.30 (d, 2H, ArH), δ 7.21 and 7.10 (dt, dt, 2H, 2H, ArH), δ 2.69 and 2.61 (t, t, 2H, 2H, ArCH₂—), δ 1.69-1.58 (m, 4H, ArCH₂CH₂—), δ 1.40-1.22 (m, 12H, —CH₂—), δ 0.92-0.87 (t, t, 6H, CH₃—). ¹³C NMR (CDCl₃, 100 MHz) δ 165.5, 149.3, 149.1, 140.5, 130.4, 129.4, 128.7, 127.3, 121.5, 36.2, 35.5, 31.95, 31.6, 31.32, 31.31, 29.4, 29.3, 22.8, 22.7, 14.24, 14.2.

The high performing heat transfer fluids enable design of smaller more efficient cooling systems and or ability to increase overall heat removal rates.

PCT and EP Clauses:

1. A composition for enhanced heat transfer fluid performance, said composition comprising at least one base heat transfer fluid, wherein the at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process, wherein the heat transfer process comprises a heated zone and/or a cooled zone, wherein the one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.

2. The composition of clause 1 wherein the at least one base heat transfer fluid comprises liquid crystals.

3. The composition of clause 1 wherein the at least one base heat transfer fluid comprises one or more nematic, smectic or discotic liquid crystals.

4. The composition of clause 2 wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl group or alkoxy group having from 2 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, or —CH2O—; and m and n are independently 0, 1, 2 or 3.

5. The composition of clause 2 wherein the one or more liquid crystals are represented by the formula:

6. The composition of clause 2 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.

7. The composition of clause 2 wherein the one or more liquid crystals are represented by the formula:

A-(R3)_(n)

wherein A is a mono-ring or a multi-ring aromatic group, R3 is the same or different and is a substituted or unsubstituted, hydrocarbon group having from 2 to 24 carbon atoms, and n is a value from 1 to 12.

8. The composition of clause 2 wherein the one or more liquid crystals are represented by the formula:

9. The composition of clause 2 wherein the one or more liquid crystals comprise hexakis(octylthio)benzene.

10. The composition of clause 1 wherein the at least one base heat transfer fluid has a freezing point of at least greater than −50° C. as determined by ASTM D1777-17, a boiling point of greater than 100° C. as determined by ASTM D1120-17, and a flash point of at least 50° C. as determined by ASTM D93-16a.

11. The composition of clause 1 wherein the heat transfer process is carried out at a temperature and/or pressure sufficient to cause the at least one base heat transfer fluid to undergo one or more phase changes.

12. The composition of clause 1 wherein the heat transfer process is carried out at a temperature from −40° C. to greater than 80° C., and/or a pressure from 50 MP to 500 MP.

13. A blend composition for enhanced heat transfer fluid performance, said blend composition comprising: (i) at least one base heat transfer fluid, and (ii) one or more lubricating oils comprising a Group I, Group II, Group III, Group IV, or Group V oil; wherein the at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process, wherein the heat transfer process comprises a heated zone and/or a cooled zone, wherein the one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.

14. A method for conducting heat transfer in a heating and/or cooling system, said method comprising: (a) providing a composition comprising at least one base heat transfer fluid in the heating and/or cooling system; and (b) conducting heat transfer between the at least one base heat transfer fluid and the heating and/or cooling system; wherein the least one base heat transfer fluid undergoes one or more phase changes in the heating and/or cooling system, wherein the one or more phase changes increase heat removal from the heating system and/or increase heat rejection in the cooling system, as compared to heat removal from a heating system and/or heat rejection in a cooling system having a base heat transfer fluid that does not undergo one or more phase changes.

15. A method of heat transfer comprising: (a) providing an object to be heated or cooled; and (b) transferring heat to or from the object to be heated or cooled by a composition comprising at least one base heat transfer fluid, wherein the least one base heat transfer fluid undergoes one or more phase changes, wherein the one or more phase changes increase heat removal from the object and/or increase heat rejection in the object, as compared to heat removal from an object and/or heat rejection in an object by a base heat transfer fluid that does not undergo one or more phase changes.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

1. A composition for enhanced heat transfer fluid performance, said composition comprising at least one base heat transfer fluid, wherein the at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process, wherein the heat transfer process comprises a heated zone and/or a cooled zone, wherein the one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.
 2. The composition of claim 1 wherein the at least one base heat transfer fluid comprises liquid crystals.
 3. The composition of claim 1 wherein the at least one base heat transfer fluid comprises one or more nematic, smectic or discotic liquid crystals.
 4. The composition of claim 2 wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl group or alkoxy group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, or —CH2O—; and m and n are independently 0, 1, 2 or
 3. 5. The composition of claim 2 wherein the one or more liquid crystals are represented by the formula:

or
 6. The composition of claim 2 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.
 7. The composition of claim 2 wherein the one or more liquid crystals are represented by the formula:


8. The composition of claim 2 wherein the one or more liquid crystals are selected from the group consisting of 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate and mixture Of them
 9. The composition of claim 2 wherein the one or more liquid crystals are represented by the formula: A-(R3)_(n) wherein A is a mono-ring or a multi-ring aromatic group, R3 is the same or different and is a substituted or unsubstituted, hydrocarbon group having from about 2 to about 24 carbon atoms, and n is a value from about 1 to about
 12. 10. The composition of claim 2 wherein the one or more liquid crystals are represented by the formula:


11. The composition of claim 2 wherein the one or more liquid crystals comprise hexakis(octylthio)benzene.
 12. The composition of claim 1 wherein the at least one base heat transfer fluid has a freezing point of at least greater than about −50° C. as determined by ASTM D1777-17, a boiling point of greater than about 100° C. as determined by ASTM D1120-17, and a flash point of at least 50° C. as determined by ASTM D93-16a.
 13. The composition of claim 1 further comprising one or more of a corrosion inhibitor, a thermal stabilizer, a pH stabilizer or buffer, an antiscaling agent, a viscosity modifier, or a biocide.
 14. The composition of claim 1 further comprising one or more lubricating oils to form a bimodal blend, wherein the one or more lubricating oils comprise a Group I, Group II, Group III, Group IV, or Group V oil, and mixtures thereof.
 15. The composition of claim 1 wherein the heat transfer process is carried out at a temperature and/or pressure sufficient to cause the at least one base heat transfer fluid to undergo one or more phase changes.
 16. The composition of claim 1 wherein the heat transfer process is carried out at a temperature from about −40° C. to greater than about 80° C., and/or a pressure from about 50 MP to about 500 MP.
 17. A blend composition for enhanced heat transfer fluid performance, said blend composition comprising: (i) at least one base heat transfer fluid, and (ii) one or more lubricating oils comprising a Group I, Group II, Group III, Group IV, or Group V oil; wherein the at least one base heat transfer fluid undergoes one or more phase changes in a heat transfer process, wherein the heat transfer process comprises a heated zone and/or a cooled zone, wherein the one or more phase changes increase heat removal from the heated zone and/or increase heat rejection in the cooled zone, as compared to heat removal from a heated zone and/or heat rejection in a cooled zone of a heat transfer process having a base heat transfer fluid that does not undergo one or more phase changes.
 18. A method for conducting heat transfer in a heating and/or cooling system, said method comprising: (a) providing a composition comprising at least one base heat transfer fluid in the heating and/or cooling system; and (b) conducting heat transfer between the at least one base heat transfer fluid and the heating and/or cooling system; wherein the least one base heat transfer fluid undergoes one or more phase changes in the heating and/or cooling system, wherein the one or more phase changes increase heat removal from the heating system and/or increase heat rejection in the cooling system, as compared to heat removal from a heating system and/or heat rejection in a cooling system having a base heat transfer fluid that does not undergo one or more phase changes.
 19. The method of claim 18 wherein the at least one base heat transfer fluid comprises liquid crystals.
 20. The method of claim 18 wherein the at least one base heat transfer fluid comprises one or more smectic or discotic liquid crystals.
 21. The method of claim 19 wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl group or alkoxy group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, or —CH2O—; and m and n are independently 0, 1, 2 or
 3. 22. The method of claim 19 wherein the one or more liquid crystals are represented by the formula:

or
 23. The method of claim 19 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.
 24. The method of claim 19 wherein the one or more liquid crystals are represented by the formula: A-(R3)_(n) wherein A is a mono-ring or a multi-ring aromatic group, R3 is the same or different and is a substituted or unsubstituted, hydrocarbon group having from about 2 to about 24 carbon atoms, and n is a value from about 1 to about
 12. 25. The method of claim 19 wherein the one or more liquid crystals are represented by the formula:


26. The method of claim 19 wherein the one or more liquid crystals comprise hexakis(octylthio)benzene.
 27. The method of claim 18 wherein the at least one base heat transfer fluid has a freezing point of at least greater than about −50° C. as determined by ASTM D1777-17, a boiling point of greater than about 100° C. as determined by ASTM D1120-17, and a flash point of at least 50° C. as determined by ASTM D93-16a.
 28. The method of claim 18 wherein the composition further comprises one or more of a corrosion inhibitor, a thermal stabilizer, a pH stabilizer or buffer, an antiscaling agent, a viscosity modifier, or a biocide.
 29. The method of claim 18 wherein the composition further comprises one or more lubricating oils to form a bimodal blend, wherein the one or more lubricating oils comprise a Group I, Group II, Group III, Group IV, or Group V oil, and mixtures thereof.
 30. The method of claim 18 further comprising conducting heat transfer between the at least one base heat transfer fluid and the heating and/or cooling system at a temperature and/or pressure sufficient to cause the at least one base heat transfer fluid to undergo one or more phase changes.
 31. The method of claim 18 further comprising conducting heat transfer between the at least one base heat transfer fluid and the heating and/or cooling system at a temperature from about −40° C. to greater than about 80° C., and/or a pressure from about 50 MP to about 500 MP.
 32. A method of heat transfer comprising: (a) providing an object to be heated or cooled; and (b) transferring heat to or from the object to be heated or cooled by a composition comprising at least one base heat transfer fluid, wherein the least one base heat transfer fluid undergoes one or more phase changes, wherein the one or more phase changes increase heat removal from the object and/or increase heat rejection in the object, as compared to heat removal from an object and/or heat rejection in an object by a base heat transfer fluid that does not undergo one or more phase changes. 